KR20120094804A - Cathode active material, energy storage apparatus including the same and method manufacturing the same - Google Patents

Abstract

PURPOSE: A positive electrode is provided to prevent capacity decrease, to improve lifetime of an energy storage device by preventing precipitation of metal atoms from lithium metal oxide. CONSTITUTION: A positive electrode comprises a lithium metal oxide, and a single-component metal oxide in grain boundary of the lithium metal oxide. A manufacturing method of the positive electrode active material comprises a step of preparing lithium metal oxide power(300'), a step of dispersing the lithium metal oxide powder in aqueous solution, and forming metal water oxide, a step of impregnating the metal water oxide into grain boundary(204) of the lithium metal oxide by applying energy to the aqueous solution, and a step of heat treating by separating lithium metal oxide powder, in which the metal water oxide is impregnated, from the aqueous solution.

Description

A cathode active material, an energy storage device including the same, and a method of manufacturing the same {Cathode active material, energy storage apparatus including the same and method manufacturing the same}

The present invention relates to a positive electrode active material, an energy storage device including the same, and a method for manufacturing the same, and more particularly, a positive electrode active material including a lithium metal oxide having improved thermal (high temperature) characteristics, an energy storage device including the same, and a manufacture thereof It is about a method.

Supercapacitors can be classified into Electric Double Layer Capacitors (EDLC) and Pseudocapacitors according to the type of electrode used. An electric double layer capacitor refers to a capacitor which stores energy in the storage due to the formation of an electric double layer at both electrodes using activated carbon in both the positive electrode and the negative electrode. The pseudocapacitor refers to a capacitor using a metal oxide used in a lithium secondary battery as an anode and an activated carbon used in an electric double layer capacitor as a cathode, which is also called a hybrid capacitor.

In the case of the electric double layer capacitor, since the electrical storage and discharge are caused by the physical desorption and absorption of ions according to the potential, the reaction rate is considerably fast and the charge and discharge life is very long, while the storage capacity is small. . In comparison, the hybrid capacitor uses the electrode material used in the secondary battery as the positive electrode and the material capable of forming the electric double layer at the negative electrode. Thus, the electric double layer capacitor with low storage capacity, cycle life and power density are used. It is an energy storage device that attempts to overcome the weaknesses of secondary batteries that have limitations.

However, since the metal oxide used as the anode is not stable at high temperatures (about 60 ° C.), it is decomposed to precipitate metal atoms constituting the metal oxide, resulting in a decrease in capacity and shortening the lifespan of hybrid capacitors and secondary batteries. .

It is an object of the present invention to provide a cathode active material, an energy storage device including the same, and a method of manufacturing the same, which can improve the heat resistance of a lithium metal oxide and improve the lifetime thereof.

The cathode active material according to an embodiment of the present invention includes a lithium metal oxide and a monocomponent metal oxide present at grain boundaries of the lithium metal oxide.

The lithium metal oxide may be cobalt (Co), manganese (Mn), nickel (Ni), iron (Fe), titanium (Ti), aluminum (Al), chromium (Cr), zirconium (Zr), gallium (Ga) or It may include any one or more of tungsten (W).

The lithium metal oxide may be LiCoO ₂ , LiMn ₂ O ₄ , LiMnO ₂ , LiNiO ₂ , or LiNi _1/3 Mn _1/3 Co _1/3 O ₂ .

 The monocomponent metal oxide may include any one or more of magnesium oxide, aluminum oxide, zirconium oxide or titanium oxide.

The lithium metal oxide may be LiMn ₂ O ₄ , and the monocomponent metal oxide may be magnesium oxide.

If another aspect of the present invention relates to an energy storage device, the energy storage device may include the positive electrode active material described above.

Another aspect of the present invention relates to a method for producing a positive electrode active material, the method for preparing a positive electrode active material comprises the steps of preparing a lithium metal oxide powder, dispersing the lithium metal oxide powder in an aqueous solution to produce a metal hydroxide, in the aqueous solution Impregnating the metal hydroxide with a grain boundary of the lithium metal oxide by applying energy, and separating and heat-treating the lithium metal oxide powder impregnated with the metal hydroxide in the aqueous solution.

In the preparing of the lithium metal oxide powder, the lithium metal oxide is cobalt (Co), manganese (Mn), nickel (Ni), iron (Fe), titanium (Ti), aluminum (Al), chromium (Cr) , Zirconium (Zr), gallium (Ga) or tungsten (W) may include any one or more.

In the step of preparing the lithium metal oxide powder, the lithium metal oxide may be _{LiCoO 2, LiMn 2 O 4,} LiMnO 2, LiNiO 2, or _{LiNi 1/3 Mn 1/3} Co 1/3 O 2.

Dispersing the lithium metal oxide powder in an aqueous solution and generating a metal hydroxide may include adding a metal salt and an alkali to an aqueous solution in which the lithium metal oxide powder is dispersed.

The alkali may include any one or more of NaOH, KOH, NH ₄ OH or urea.

In the dispersing the lithium metal oxide powder in an aqueous solution and producing a metal hydroxide, the metal hydroxide may include any one or more of magnesium hydroxide, titanium hydroxide, aluminum hydroxide or zirconium hydroxide.

Impregnating the metal hydroxide with the grain boundaries of the lithium metal oxide by applying energy to the aqueous solution may include any one or more of milling the aqueous solution, applying an ultrasonic wave to the aqueous solution, or applying thermal energy.

In the step of separating and heat-treating the lithium metal oxide powder impregnated with the metal hydroxide in the aqueous solution, the heat treatment may be performed at 300 ℃ ~ 900 ℃.

The positive electrode active material of the present invention, an energy storage device including the same, and a method of manufacturing the same, impregnate a single component metal oxide in the grain boundary of the lithium metal oxide to prevent precipitation of metal atoms from the lithium metal oxide, thereby preventing capacity reduction and saving energy. The life of the device can be extended, and it can be used for a long time even at high temperature.

1 is a conceptual diagram illustrating the operation of a hybrid capacitor using a cathode active material according to an embodiment of the present invention.
2 and 3 are a flow chart and a conceptual diagram showing a method of manufacturing a positive electrode active material according to an embodiment of the present invention, respectively.

The present invention relates to a positive electrode active material. The positive electrode active material includes a monometallic metal oxide present at a grain boundary of lithium metal oxide and the lithium metal oxide. In the present invention, the monocomponent metal oxide refers to a metal oxide (except lithium oxide) in which one metal atom exists.

The lithium metal oxide is a metal oxide containing lithium (Li). In addition to lithium, it may further include one or more metals. Specifically, in addition to lithium (Li), cobalt (Co), manganese (Mn), nickel (Ni), iron (Fe), titanium (Ti), aluminum (Al), chromium (Cr), zirconium (Zr), gallium ( Ga) or tungsten (W) may be a lithium metal oxide containing at least one. More specifically, LiCoO _2, may be _{LiMn 2 O 4, LiMnO 2,} LiNiO 2, or _{LiNi 1/3 Mn 1/3} Co 1/3 O 2.

Metal oxides including lithium metal oxides may exist as single crystals, but are usually present in a polycrystalline (polycrystal) state. That is, it consists of a grain boundary of the boundary between a single crystal and the single crystal. In the positive electrode active material made of lithium metal oxide, there is a problem in that the metal atoms (metal atoms other than lithium atoms) constituting the lithium metal oxide are usually precipitated at a high temperature and thus the capacity thereof is lowered. In order to prevent this, the positive electrode active material of the present invention has a structure in which the monocomponent metal oxide is impregnated in the grain boundary of the lithium metal oxide. That is, the mono-component metal oxide can prevent the deposition of metal atoms constituting the lithium metal oxide to improve the life of the energy storage device.

Although there is no limitation on the monocomponent metal oxide, a metal oxide having a high melting point is preferable for improving heat resistance. For example, a metal oxide including any one or more of magnesium oxide (magnesia, MgO), aluminum oxide (alumina, Al ₂ O ₃ ), zirconium oxide (zirconia, ZrO ₂ ) or titanium oxide (titania, TiO ₂ ) Can be.

Another aspect of the invention relates to an energy storage device. That is, it may be used in an energy storage device such as a hybrid capacitor and a secondary battery using the cathode active material described above.

1 is a conceptual diagram illustrating the operation of a hybrid capacitor using a cathode active material according to an embodiment of the present invention. As shown, the hybrid capacitor may have an asymmetric electrode structure in which the negative electrode material and the positive electrode material are formed of different materials. A material including activated carbon may be used as the negative electrode 102 of the hybrid capacitor, and the positive electrode 104 may include a cathode active material made of lithium metal oxide in which a single component metal oxide is present at a grain boundary thereof. Specifically, a metal oxide (lithium metal oxide) including lithium (Li) may be used.

A hybrid capacitor having an asymmetric electrode structure is formed by intercalation and deintercalation in which lithium ions in an electrode including a lithium metal oxide are intercalated or extracted between molecules of a positive electrode 104 material. It acts as a mixing mechanism of the operation mechanism of lithium ion battery using chemical reaction and the operation mechanism of electric double layer capacitor.

An electric double layer is a bilayer composed of dipoles, in which positive and negative charges are continuously distributed on the one side and the other side in the thin film layer of an object, with the same surface density. In the negative electrode 102, a charge is adsorbed to the electric double layer on the interface between the electrode surface and the electrolyte to store electrical energy, and to detach and release energy. In the positive electrode 104, lithium ions move from the negative electrode to the positive electrode to store energy through intercalation and deintercalation of lithium ions as described above, and move energy from the positive electrode to the negative electrode. Use to emit.

As an electrolyte, in order to use the mechanism of a lithium ion battery, lithium salts such as lithium fluorophosphate (Lithium Fluorophosphate, LiPF ₄ ), lithium fluoroborate (Lithium Fluoroborate, LiBF 4), lithium perchlorate (LiClO ₄ ), etc. Any one or more, such as ethylene carbonate (C ₃ H ₄ O ₃ ), dimethyl carbonate (C ₃ H ₆ O ₃ ), or diethyl carbonate (C ₅ H ₁₀ O ₃ ) Organic solvents can be used.

In order to use the mechanism of the electric double layer capacitor, an aqueous solution or an organic electrolyte is used, but considering the pore size of the activated carbon is approximately 2nm, excellent charge and discharge characteristics and high capacity can be obtained only when the salt size is appropriate. In one example, tetraethylammonium Tetrafluoroborate (C ₈ H ₂ 0NBF ₄ ), or the like in propylene carbonate (Propylene Carbonate, C ₄ H ₆ O ₃ ) or acetonitrile (Acetonitrile, CH ₃ CN) as an electrolyte Tetraalkylammonium Salt can be dissolved and used. In another example, butylmethylpyrrolidinium, ethynmethylpyrrolidinium, and dimethylpyrrolidinium (Dimethyl) are used as electrolytes. Solutes made of pyrrolidinium salts, such as Pyrrolidinium), include propylene carbonate (Propylene Carbonate), ethylene carbonate (Ethylene Carbonate), dimethyl carbonate (Dimethyl Carbonate), diethyl carbonate (Ethyl Methyl Carbonate) It can be used by mixing in the solvent containing any one or more of). In another example, the electrolyte is a solute made of pyrrolidinium salts such as butylmethylpyrrolidinium, ethynmethylpyrrolidinium and dimethylpyrrolidinium, and tetraethylammonium tetrafluoroborate and ethylmethylimidazolium tetrafluoro. Solute mixed with ammonium salts such as borate, tetraethylammonium hexafluoroborate, tetraethylammonium perchlorate and the like is added to a solvent containing at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate. It can be mixed and used.

As described above, the hybrid capacitor uses both the mechanism of the lithium ion battery and the mechanism of the electric double layer capacitor, and thus, the electrolyte of the lithium ion battery and the electrolyte of the electric double layer capacitor may be mixed and used.

The plurality of supercapacitors may be connected in series so as to have a large charging capacity and a charging voltage in series to increase the discharge voltage, or may be connected in parallel to increase the capacity. In addition, it is also possible to form and use a supercapacitor module in which a plurality of supercapacitors are connected in parallel in order to increase voltage and increase capacity.

Hybrid capacitors using the above-mentioned electrode materials and electrolytes have almost no leakage current, and thus have excellent energy storage capability, and above all, precipitation of metal atoms constituting lithium metal oxide at high temperature is suppressed, and therefore, desert areas and tropical areas. Even if used in the area, it can be used for a long time without changing the capacity characteristics.

Another aspect of the invention relates to a method for producing a cathode active material. 2 and 3 are a flow chart and a conceptual diagram showing a method of manufacturing a positive electrode active material according to an embodiment of the present invention, respectively.

2 and 3, first, a lithium metal oxide powder is prepared (S102). The lithium metal oxide is a metal oxide containing lithium (Li) as described above. In addition to lithium, it may further include one or more metals. Specifically, in addition to lithium (Li), cobalt (Co), manganese (Mn), nickel (Ni), iron (Fe), titanium (Ti), aluminum (Al), chromium (Cr), zirconium (Zr), gallium ( Ga) or tungsten (W) may be a lithium metal oxide containing at least one. More specifically, LiCoO _2, may be _{LiMn 2 O 4, LiMnO 2,} LiNiO 2, or _{LiNi 1/3 Mn 1/3} Co 1/3 O 2.

The lithium metal oxide powder may be prepared by various methods such as solid phase synthesis, vapor phase synthesis, liquid phase precipitation, and sol-gel. For example, when LiMn ₂ O ₄ is used as the positive electrode active material, LiMn ₂ O ₄ powder is prepared by a sol-gel method using manganese nitrate or manganese acetate, lithium hydroxide (LiOH), and ammonia water (NH ₄ OH). can do.

Next, the lithium metal oxide powder is dispersed in an aqueous solution to produce a metal hydroxide (S104). The metal hydroxide may be determined depending on the monocomponent metal oxide to be finally impregnated into the grain boundary of the lithium metal oxide. For example, magnesium hydroxide (Mg (OH) ₂ ) if the monocomponent metal oxide is magnesium oxide, titanium hydroxide (Ti (OH) ₄ ) if the monocomponent metal oxide is titanium oxide, and aluminum hydroxide if the monocomponent metal oxide is aluminum oxide (Al (OH) ₃ ), and may be zirconium hydroxide (Zr (OH) ₄ ) when the monocomponent metal oxide is zirconium oxide. Alternatively, any two or more of the metal hydroxides may be included.

To produce metal hydroxides, metal salts and alkalis may be added to the aqueous solution in which the lithium metal oxide powder is dispersed. For example, in order to produce magnesium hydroxide, a metal salt including any one or more of MgCl ₂ , Mg (NO ₃ ) _2, or MgSO ₄ may be used, and the alkali may be NaOH, KOH, NH ₄ OH, or urea. An alkali containing any one or more of these can be used. In another example, in order to produce titanium hydroxide, TiCl ₄ , Ti (NO ₃ ) ₄ , Ti (SO ₄ ) ₂ , or the like may be used as the metal salt, and the alkali may be NaOH, KOH, NH ₄ OH, or urea. An alkali containing any one or more of these can be used. For another example, to produce zirconium hydroxide, ZrCl ₄ , Zr (NO ₃ ) ₂ , Zr (NO ₃ ) ₄ , Zr (SO ₄ ) _2, etc. may be used as the metal salt, and NaOH, KOH, NH Alkali containing at least one of ₄ OH or urea can be used.

Next, energy is applied to the aqueous solution to impregnate the metal hydroxide with the grain boundaries of the lithium metal oxide (S106).

There is no limitation on the method of applying energy to the aqueous solution. For example, the method may include any one or more of a method of applying ultrasonic waves, a method of ball milling, or a method of applying thermal energy. The method of applying the ultrasonic wave may use a sonicator, sonicleaner, and the like, and the ball mill may use a ball of several mm to several tens of mm, a rotation speed of several tens to several hundred rpm, and a ball mill for one to hundred hours. . In addition, heat energy may be applied to a hot plate and a vortex may be formed in the aqueous solution using a stirrer.

By applying energy to the aqueous solution in this manner, the metal hydroxide 300 can be impregnated in the grain boundary 204, which is a boundary between the grains 202 of the lithium metal oxide.

Next, the lithium metal oxide powder impregnated with the metal hydroxide in an aqueous solution is separated and heat treated (S108).

Through heat treatment, OH may be released from the metal hydroxide 300 to H ₂ O or the like, and the metal hydroxide 300 may be transformed into the metal oxide 300 ′. To this end, the metal hydroxide may be heat treated above a temperature at which the metal hydroxide may phase change into a metal oxide. For example, heat treatment may be performed at 300 ° C or higher, preferably 300 ° C to 900 ° C, and more preferably 300 ° C to 600 ° C. The heat treatment temperature range can be more clearly determined from thermogravimetric analysis (TGA) of the metal hydroxide, differential scanning calorimeter (DSC) data, and the like. That is, by heat treatment in the temperature range of 300 ℃ to 600 ℃, impurities, H ₂ O, etc. are discharged from magnesium hydroxide, titanium hydroxide, aluminum hydroxide, zirconium hydroxide and the like to magnesium oxide, titanium oxide, aluminum oxide, zirconium in the grain boundary of lithium metal oxide Oxides and the like may be left. Alternatively, any two or more of the metal oxides may be left.

Heat treatment may be carried out in a conventional firing furnace or a furnace (furnace), and may be heat treated in an air atmosphere or an oxygen atmosphere.

Capacitors such as hybrid capacitors, secondary batteries, etc. may be manufactured using the cathode active material prepared as described above, and may be used for various industrial and home electronic devices.

102 negative electrode 104 positive electrode
202: grain 204: grain boundary
300: metal hydroxide 300 ': metal oxide

Claims (14)

Lithium metal oxides; And
Monocomponent metal oxides present in the grain boundaries of the lithium metal oxides
A positive electrode active material comprising a.
The method of claim 1,
The lithium metal oxide may be cobalt (Co), manganese (Mn), nickel (Ni), iron (Fe), titanium (Ti), aluminum (Al), chromium (Cr), zirconium (Zr), gallium (Ga) or A positive electrode active material which is a metal oxide containing any one or more of tungsten (W).
The method of claim 1,
The lithium metal oxide is LiCoO ₂ , LiMn ₂ O ₄ , LiMnO ₂ , LiNiO ₂ , or LiNi _1/3 Mn _1/3 Co _1/3 O ₂ positive electrode active material.
The method of claim 1,
The monocomponent metal oxide may include at least one of magnesium oxide, aluminum oxide, zirconium oxide, and titanium oxide.
The method of claim 1,
The lithium metal oxide is LiMn ₂ O ₄ , the monocomponent metal oxide is a magnesium oxide positive electrode active material.
An energy storage device comprising the cathode active material of any one of claims 1 to 5.
Preparing a lithium metal oxide powder;
Dispersing the lithium metal oxide powder in an aqueous solution to produce a metal hydroxide;
Impregnating the metal hydroxide with a grain boundary of the lithium metal oxide by applying energy to the aqueous solution; And
Separating and heat-treating the lithium metal oxide powder impregnated with the metal hydroxide in the aqueous solution
Cathode active material manufacturing method comprising a.
The method of claim 7, wherein
In the preparing of the lithium metal oxide powder, the lithium metal oxide is cobalt (Co), manganese (Mn), nickel (Ni), iron (Fe), titanium (Ti), aluminum (Al), chromium (Cr) , Zirconium (Zr), gallium (Ga) or tungsten (W) metal oxide containing any one or more methods of producing a positive electrode active material.
The method of claim 7, wherein
In the step of preparing the lithium metal oxide powder, wherein the lithium metal oxide is _{LiCoO 2, LiMn 2 O 4,} LiMnO 2, LiNiO 2, or _{LiNi 1/3 Mn 1/3} Co 1/3 O 2 of the positive electrode active material .
The method of claim 7, wherein
Dispersing the lithium metal oxide powder in an aqueous solution and producing a metal hydroxide may include adding a metal salt and an alkali to an aqueous solution in which the lithium metal oxide powder is dispersed.
The method of claim 10,
The alkali is a positive electrode active material manufacturing method comprising any one or more of NaOH, KOH, NH ₄ OH or urea.
The method of claim 7, wherein
Dispersing the lithium metal oxide powder in an aqueous solution and producing a metal hydroxide, wherein the metal hydroxide comprises any one or more of magnesium hydroxide, titanium hydroxide, aluminum hydroxide or zirconium hydroxide.
The method of claim 7, wherein
Impregnating the metal hydroxide with the grain boundaries of the lithium metal oxide by applying energy to the aqueous solution may include preparing at least one of milling the aqueous solution, applying ultrasonic waves to the aqueous solution, and applying thermal energy. Way.
The method of claim 7, wherein
In the step of separating and heat treating the lithium metal oxide powder impregnated with the metal hydroxide in the aqueous solution, the heat treatment is performed at 300 ℃ ~ 900 ℃.

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